The present invention relates to a method of excavating an underground area from a working gallery beneath the area for excavation. The equipment of the invention is specially adapted to allow for excavation without human intervention in the excavation area, thereby allowing for the excavation of a hazardous area without exposing humans to the hazards.
The equipment of the invention represents a novel adaption of jet boring technology. Thus its use is confined to excavations of underground areas that are susceptible to disaggregation by high pressure jetting action. Such areas tend to have weak goetechnical characteristics, and may be prone to cave-in or flooding during excavation. Additionally, the equipment of the invention would only be for use when it is considered to be advantageous to access the excavation area from below rather than directly from the surface. For example, access from the surface may be particularly difficult if the area for excavation underlies a lake which imposes high hydrostatic pressure on the area.